test: introduce SetUpTestCase/TearDownTestCase

This commit add SetUpTestCase and TearDownTestCase functions that will
be called once per test case. Currently we only have SetUp/TearDown
which are called for each test.

This commit moves the initialization and configuration of Node and V8 to
be done on a per test case basis, but gives each test a new Isolate.

PR-URL: https://github.com/nodejs/node/pull/18558


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>